Remove node-redis from documentation

[nwalters512]

My team runs multiple servers and uses https://github.com/socketio/socket.io-redis-adapter to ensure messages can be delivered to all clients, no matter which server they're actually connected to. Recently, we got reports from users that updates were not in fact being delivered successfully to clients. After a solid day of debugging, we discovered that our Redis clients were unexpectedly disconnecting from the Redis server. We use node-redis as our Redis client, and by default it should reconnect to the Redis server. It was in fact reconnecting, but after reconnecting, it failed to re-establish the subscription.

This appears to be a well-documented problem with node-redis specifically:

• Keyspace notifications are lost after reconnection redis/node-redis#2155
• Subscriptions do not receive data after reconnect redis/node-redis#1252

Other folks have moved off node-redis to ioredis because of this (see mastodon/mastodon#25157). ioredis explicitly documents that they restore subscriptions after reconnecting:

When reconnected, the client will auto subscribe to channels that the previous connection subscribed to.

Given that socket.io's Redis adapter relies almost exclusively on pub/sub capabilities of Redis clients, I'd like to propose that socket.io remove node-redis from its documentation in favor of recommending just ioredis. At the very least, a warning about this issue with node-redis should be added.

For reference, here's where this is currently documented: https://socket.io/docs/v4/redis-adapter/.

Perhaps I should have filed this in https://github.com/socketio/socket.io-website. Let me know if that's the case and I can move the issue there.

[darrachequesne]

Hi! Thanks for the heads-up 👍

I've added a note in the documentation: https://socket.io/docs/v4/redis-adapter/#with-the-redis-package